1220511561 has 4 divisors (see below), whose sum is σ = 1627348752. Its totient is φ = 813674372.

The previous prime is 1220511553. The next prime is 1220511587. The reversal of 1220511561 is 1651150221.

1220511561 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1220511561 - 2³ = 1220511553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1220511361) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 203418591 + ... + 203418596.

It is an arithmetic number, because the mean of its divisors is an integer number (406837188).

Almost surely, 2^1220511561 is an apocalyptic number.

It is an amenable number.

1220511561 is a deficient number, since it is larger than the sum of its proper divisors (406837191).

1220511561 is an equidigital number, since it uses as much as digits as its factorization.

1220511561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406837190.

The product of its (nonzero) digits is 600, while the sum is 24.

The square root of 1220511561 is about 34935.8206000661. The cubic root of 1220511561 is about 1068.6790584969.

Adding to 1220511561 its reverse (1651150221), we get a palindrome (2871661782).

The spelling of 1220511561 in words is "one billion, two hundred twenty million, five hundred eleven thousand, five hundred sixty-one".